Security door with improved sensor for detecting unauthorized passage

ABSTRACT

A control system for a revolving door includes an ultrasonic sensor having multiple sensor heads. The door has a housing, and multiple moveable compartments formed by door wings attached to and radially extending from a rotatable axis. The sensors emit energy waves into the housing in bursts, then receive echoes from any objects, including people, in the chambers. The sensors are activated when the door is activated by an authorized user. A controller stores a binary &#34;echo&#34; or &#34;no echo&#34; signal in memory in response to an emitted energy wave. The memory is formed by multiple arrays, each array having a column associated with a particular sensor and used for storing echo signals from a particular ultrasonic burst. Each bit in a column represents incremental ranges of objects from the sensors head, and the controller stores the &#34;echo&#34; or &#34;no echo&#34; signal in an appropriate bit based on the elaspsed time from the preceding burst. To avoid interference from reverberations, the burst cycle time is varied, the amount of time following each burst is sufficiently greater than the time for receiving an echo from the floor of the housing so that reverberations will die down, and multiple arrays of echo data are filled with corresponding results and ANDed together to form a results array. The controller uses the results array to determine whether there is an object in an unauthorized chamber. The system also ignores signals which are given from the top of a door wing passing by a sensor head.

BACKGROUND OF THE INVENTION

This invention relates generally to security passageways, andparticularly to security doors and the sensing of unauthorized passageof objects as well as people through the doors.

Security doors are used in airports, banks, commercial buildings,military installations, and other locations where restricted access isdesirable. One type of security door is a revolving door with aplurality of passenger compartments defined by panels. For example, sucha revolving door is disclosed in U.S. Pat. No. 4,627,193 issued on Dec.6, 1986. Normally, in this type of door a person inserts a pass cardinto a card identifying device linked with a control mechanism for thedoor, then enters a compartment on one side of the door. If the card isauthorized, the door will turn its panels and thus each compartmentuntil the entered compartment moves from the entrance to the exit. Asthe entered compartment passes from the entrance to the exit, all of theother compartments move by a corresponding amount. Therefore, it ispossible for an unauthorized person to "tailgate", i.e., to either enterthe compartment immediately following the authorized party as it passesthe entrance, or enter a compartment located at the exit. In the formersituation, the unauthorized party will get trapped in the doorway whenthe door stops. If the door has a "trapped man" feature to detect such asituation, the system will reversely rotate the door after stopping toforce the unauthorized "trapped" person back to his starting point. Ifthe door is not equipped with such a "trapped man" feature, the nextauthorized party to enter the doorway will allow the unauthorized partyto pass to the exit. In the situation where the "tailgater" isattempting to pass from the exit to the entrance, the system may alsodetect him and return him to his starting point before allowing hiscompartment to reach the entrance.

One way that tailgating has been detected is by the use of floor mats inthe security door to detect when a compartment has been entered.However, such mats have several drawbacks. First, rain, snow, dirt orother foreign matter can often cause mat failures. Second, a mat cannotdetect a person or object such as a gun or a security pass card attachedto the door frame. Third, it is difficult to make a mat sufficientlysensitive to lightweight objects. Accordingly, there is a need to moreaccurately and reliably detect whether unauthorized parties or objectshave entered a compartment of a revolving security door.

It has been proposed to use ultrasonic sensors instead of mats, but useof such sensors in a revolving door presents difficult problems. First,the sensors must distinguish between door panels and people or objects.If the sensors are merely turned off when the door panel passes by,objects attached to or close to the door panel can get through thedoorway undetected. Second, to detect small objects such as pass cardsor firearms, the sensors must have a high gain. Such a high gainincreases the likelihood that reverberations or echoes will cause falsereadings. This is especially true in a security revolving door which hasa substantially closed housing. Similarly, the greater the range(portion of the floor to ceiling distance) covered by the sensor, thegreater the likelihood of false readings due primarily to echoes fromthe floor. Accordingly, floor mats have been popular in security doordevices.

SUMMARY OF THE INVENTION

The invention is an improved sensor system for a security door toprevent unauthorized entry to or exit from a secured area. The inventionis also a security door including the improved sensor system. The sensorsystem improves security by greatly enhancing the ability to detectunauthorized persons or objects located in a compartment of the door.

In one embodiment, the security door has a housing having an entranceinto and an exit from a room. The door includes a central shaft or thelike rotatably disposed in the housing and supporting a plurality ofpanels or wings which, in cooperation with the housing, define at leastone compartment rotatable with the shaft to transport a person betweenthe entrance and exit. The door has a control system which includes amain microprocessor that receives inputs from an identificationmechanism such as a card reader and a sensor system and outputs signalsto control the door. The control system includes a mechanism forrotating the shaft thereby moving a selected compartment between theentrance and exit in response to identification of an authorized person.As the shaft rotates, the control system keeps track of the position ofthe authorized chamber.

To establish the progression of the authorized person through the door,the sensor system preferably includes another microprocessor andultrasonic or other energy sensors for detecting physical objectsgenerates a signal as the authorized person passes through a designatedregion of the housing. This sensing system will also detect when aperson or object is in another compartment. Should the mainmicroprocessor determine that the position of the compartment and thegeneration of the signal indicate that an unauthorized person or objectis in another compartment, the microprocessor will issue a disablingcommand to prevent further forward movement of all compartments. Thedisabling command may brake and hold the shaft against rotation, mayenable only reverse movement of the compartment to discharge the personwithin the compartment, or may actually reverse the rotation of theshaft to forcibly discharge all individuals from the door.

In a preferred embodiment, the ultrasonic sensors are located on theceiling of the door housing for irradiating waves in a generally conicalshape downward into the housing. At least two sensors or two sets ofsensors are located on the ceiling of the door housing for detectingunauthorized movement of persons or objects from the entrance to theexit as well as from the exit to the entrance. The microprocessorcontrolling the sensors ignores signals from the door frame yet reactsto signals from objects in those compartments for which passage has notbeen authorized.

In the preferred embodiment, the sensor controller sends signals to thesensors causing them to emit bursts of ultrasonic waves. The sensorsdetect echoes of the emitted waves. The controller samples the echoes atpredetermined times following a burst and stores a "1" or "0" in anarray of memory in response to detection of an echo or no echo. Eacharray is organized by columns of bits, each column being associated withone sensor, and each bit in the column corresponding to a predeterminedelapsed time from a particular ultrasonic burst. Corresponding bits incorresponding columns of each array are ANDed together to reduce thelikelihood of a false echo from ghosts caused by any reverberations ofechoes. Moreover, burst frequency is preferably varied so that anyghosts will be stored in different bits for different arrays, and willthus be cancelled out by the ANDing process. The amount of time betweenbursts is preferably sufficient to allow reverberations to die out. Inrevolving doors where it is possible for echoes or reverberations fromone chamber to be detected by sensors in other chambers, bursts fromsensor(s) in each compartment are staggered to avoid or minimize suchinterference.

When unauthorized passage is detected, the control system preferablystops the doorway before the unauthorized person or object can gainpassage therethrough, and initiates reverse rotation to move theunauthorized person or object to the place, i.e., the entrance or exit,where it embarked.

The use of such sensors enables the control system to detect not onlylarge objects such as people, but also very small items at substantiallyany location within a compartment to accurately and reliably detect"tailgating." In a further embodiment, additional ultrasonic sensors areprovided to detect trapped objects in the event that the doorway stopswith a person or object in a compartment that is not located at anentrance or exit.

The above features and advantages of the invention, as well asadditional features and advantages will be appreciated and betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a security door incorporating sensorsand a control scheme according to the present invention;

FIG. 2 is a view of the underside of the top of the security door ofFIG. 1 to illustrate placement of the sensors;

FIG. 3 is a schematic showing major components of the security doorcontrol system;

FIGS. 4a and 4b are waveform diagrams of the energy waves emitted by andreflected toward the sensor;

FIG. 4c is a waveform diagram of energy waves emitted by the sensor;

FIG. 5 is a schematic of the memory used in the control system accordingto the invention; and

FIG. 6 is a flowchart showing the inventive control scheme.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The control and sensor system for a security door according to theinvention operate together to detect the presence of unauthorizedpersons (or objects) attempting to gain passage through the door by"tailgating." When tailgating is detected, the control system willprevent the unauthorized person from passing through by stopping thedoor. In a preferred embodiment, the door will then be reversed toforcibly move the unauthorized user to the entrance or exit at which heentered the door.

FIG. 1 shows a security door 20 with sensors and a control systemaccording to the present invention. Preferably, the security door 20 isa revolving type. The door is incorporated into a wall 22 whichseparates a security area 24 from a general access or lesser securityarea 26. The wall 22 with the door 20 functions as a security barrierbetween areas 24 and 26.

The door has a cylindrical housing 28 which includes upstanding,semi-cylindrical panels 30. The panels 30, as shown in FIGS. 1 and 2,extend between a circular bottom 32 and a top 42. The panels preferablyspan approximately 90° of arc. Each panel 30 is fashioned from a pair ofsemi-cylindrical segments (such as glass) connected between andsupported by edge posts 36, a center post 38, and a bottom skirt 40secured to the bottom 32. The posts 38 are connected to the wall 22 toincorporate the panels 30 into the wall structure. The semicylindricalsegments may be fashioned from various materials including standard orsafety glass, bullet-proof glass, acrylic or solid bars as desired.

The top 42 is typically disposed in or incorporated into the ceiling(not shown) of the facility. The panels 30, top 42, and bottom 32cooperate to define cylindrical housing 28 having two arcuate portals,an entrance 44 in general access area 26 and an exit 46 in security area24.

To prevent unauthorized persons from passing from entrance 44 throughhousing 28 to exit 46, door 20 includes a revolving door member 48disposed in the housing (see FIG. 2). Revolving door member 48 has arotatable shaft 50 supported between the top 42 and bottom 32 centeredalong the axis of revolution of the door. The top 42 has an axialopening (not shown) through which shaft 50 protrudes. Four wings 52project outwardly from shaft 50 and are of sufficient length to sweepclose to semi-cylindrical panels 30 While door 20 preferably has fouridentical panels or wings 52 spaced roughly 90° from one another, moreor fewer panels could be used as desired. The four spaced panels 52cooperate with housing 28 to define four rotatable pie-slice-shapedcompartments. A person desiring to move from one of the areas 24,26 tothe other enters a selected compartment and travels therewith betweenentrance 44 and exit 46.

Door 20 includes a drive system 60 which comprises an electric motor, amotor multiplier and a gear reducer such as described in U.S. Pat. No.4,627,193, hereby incorporated by reference. Drive system 60 is coupledto revolving door member 48 so that operation of the drive systemrotates member 48.

The door wings 52 each include a rectangular frame 70 supporting a pane72. The frame 70 has a length to project from the shaft 50 to sweepclosely to the semicylindrical panels 30 as the member 48 revolves and aheight to extend from a location near the bottom 32 to a position nearthe top 42. Accordingly, the wings 52, in cooperation with the housing28, define the compartments.

The wings 52 can be formed many different ways. For example, the wingsneed not be solid panes, but can be formed by bars, grating or the like.

To prevent unauthorized ingress and egress from security area 24, acontrol system is provided to perform the appropriate regulation. In thedisclosed embodiment, the control system according to the invention islocated in a box 94 on the top 42 of housing 28. While the followingdescription is (for purposes of explanation) primarily directed towardunauthorized entry into security area 24, the description is equallyapplicable to the situation wherein unauthorized items includingpersonnel attempt to exit the security area.

As shown in FIG. 3, the control system includes a main processor 194, acontroller 294 and supporting peripheral hardware housed withinenclosure 94 for controlling the starting, stopping and directionalrotation of the motor and shaft which turn the compartments. As aspecific example of the preferred embodiment, the main processor is anIntel 8749 or 8751 microprocessor manufactured by Intel Corporation andthe controller is a Zilog Z8 microprocessor manufactured by ZilogCorporation. The peripheral hardware includes a memory 394 sufficientlylarge to perform calculations and control functions which willhereinafter become apparent, for example, a random-access memory (RAM).Suitable types and sizes of memory will be evident to one of ordinaryskill and will depend upon the desired speed and accuracy of thedetection system and the various memory management techniques adopted.

The main processor 194 includes or is linked to a mechanism whichdetermines door position, e.g. by using a pulse generator as set forthin U.S. Pat. No. 4,627,193. In that patent, door position is tracked byusing a cam and a cam follower, which has its motion translated by aproximity sensor into pulses which occur at each predetermined incrementof door rotation, e.g., 3°. This mechanism is represented in FIG. 3herein by position detection system 197. The pulses are recorded by acounter, which is read by the main processor 194. The value on thecounter corresponds to a specific amount of door rotation. When the doorcompletes 180° of rotation, i.e. the point in the present embodimentwhere the entered compartment has moved to the exit compartment, anotherproximity detector in the position detection system 197 indicates suchmovement to the main processor 194, and the processor stops drive system60 and resets the counter. The control system also includesidentification devices 110, 114 such as card readers or other means foridentifying an authorized user to initiate the entry sequence andanti-jam features as set forth in that same patent.

In the present invention, to detect people or objects, the door includesan array of sensors 99a-99h, preferably arranged in a circular patternaround the ceiling of the housing as depicted in FIG. 2. It is preferredto mount the sensors on the ceiling rather than the floor where they maybe stepped on or subjected to rain, water, snow, dirt or otherundesirable environmental conditions. Nevertheless, with appropriateenvironmental protection, the sensors are also mountable on the floor.

The sensors radiate energy waves, preferably ultrasonic, in a generallyconical shape and detect the echoes of the waves reflected from anyphysical surfaces encountered. Having multiple concentric arrays of thesensors around center post-axis 24 allows greater coverage of the areain the compartment. Preferably, each circle includes at least one sensorfor each compartment, each sensor being placed at an angulardisplacement about the center post-axis identical to that of the angledefined by any two adjacent door panels 52. In the illustrated revolvingdoor, adjacent panels meet at 90° so that the sensors are separated by90°. Although this geometry is preferred, there are many otherconfigurations and numbers of sensors which will provide suitablecoverage of the housing and which fall within the spirit and scope ofthe invention.

In general, operation takes place as follows: Once an authorized userhas been identified by the card reader 110 or 114, the main processor194 activates the position detection system 197 and also activates drivesystem 60 to revolve the compartments. At the same time or substantiallycontemporaneously, the main processor 194 instructs controller 294 toactivate sensors 99a-99h to detect non-empty compartments. The sensorsemit bursts of ultrasonic waves and detect return echoes from objectsincluding people. FIG. 3 shows controller 294 in association with memory394 and sensor 99a. Connection with and operation of the other sensorsare the same.

In particular, sensor 99a receives at preset time intervals a digitalwaveform A₁ from the controller having a frequency in the ultrasonicrange. The sensor has a transmitter 199a, which includes an amplifierfor translating the electrical waveform into successive bursts ofultrasonic acoustical waves directed from the sensor head toward thefloor of each compartment. Each sensor head also includes a receiver299a having a sense amplifier for detecting return echoes of the waves.The transmitter and receiver are typically dormant when there is noattempted passage through the revolving door. That is, signal A₁ is notbeing generated or sent.

During attempted passage, the transmitter and receiver are activated bycontroller 294 which sends signal A₁ and also a signal GC₁ adjusting thegain of the sense amp to an amount appropriate for receiving the echoes.Preferably, the gain of the sense amp is increased over time bycontrolling the time period between each clock signal in signal GC₁. Inother words, the gain clock signal selectively increments the gain ofthe receiver in digital steps, which may be set and implemented by usingan integrated circuit in the sensor head. Each pulse on the gain clockline increments a counter in the sense amp in receiver 299a to selectthe next highest incremental gain step. The counter is reset to thefirst, i.e. lowest gain step, by a burst signal. Control of the timespacing between gain clock pulses determines the rate of increase ofgain with time following the burst, and eliminates the need fordifferent sensor heads for different environments. A suitable gain clocksignal is active low and is approximately 15 microseconds wide.

The amount of increase of gain with respect to time may be selected andset at installation based primarily on the door structure. For example,in a door with highly polished or mirror-like surfaces, a smaller gainwith time is appropriate than in a door with a textured rubber floor,and bar-like door wings.

The bursts A₁ through A₈ are typically relatively short, e.g. 0.5 ms,and drive the ultrasonic transmitter at a frequency on the order of 48kHz, but this frequency may vary as explained below. Preferably, thebursts are active low.

After each burst, the controller 294 waits a predetermined period oftime so that the sense amp in sensor 99a can receive the echoes of anyobjects the burst encounters. This "echo receive time" is at least aslong as the maximum desired distance d set for the sensors to detectobjects in the chambers. For example, in a typical door with afloor-to-ceiling distance of 8', d could be set to 7' (12" above thefloor). The echo receive time is determined empirically, e.g., when thedoor is installed, or is calculated based on the speed of the ultrasonicwaves. Preferably, the time between bursts is set greater than the echoreceive time, so that any reverberations will die out or substantiallydie out by the next burst. In addition, interference from other chamberswill be minimized.

The echoes are received by the sense amps in sensors 99a through 99h inreal time, and the gain of the sense amps is controlled over this timeto effectively convert the echoes into digital signals B₁ through B₈.The sense amps simply are "go"/"no go" detectors that pass a single bitdigital signal B₁ to an input port of the controller 294.

One of the problems with using sensors in a relatively closed structuresuch as a revolving door is noise from echo reverberation causing falsedetection of objects. The present invention solves this problem in anovel way. The problem of echo reverberation is shown in FIG. 4A. Whenthe bursts have a constant cycle rate, "ghost" echoes of an initial echooccur due to multiple reflections, especially in a closed chamber andespecially where the energy waves are sufficiently powerful to enabledetection of small or soft objects. The ghosts will be received at thesame elapsed time following each particular burst. To avoid readingthese ghosts as true echoes, the system is modified in two ways. First,the burst cycle time is varied, as shown in FIG. 4B. This causes ghoststo be misaligned. Second, the detected echoes following each burst arestored (in memory 394 shown in detail in FIG. 5 as explained below) inrelation to the elapsed time from the most recent burst, and the echoesfrom (at least) the last two bursts are logically ANDed to obtain aresults array R. Any echoes that occur at the same time interval afterboth the last two bursts will result in a "1." Otherwise, the result is"0" for that time interval. As shown in FIG. 4A, where the cycle timesdo not vary, ghosts will occur in cycles 2 and 3 at the same elapsedtime, causing an erroneous detection. However, as shown in FIG. 4B, theghosts do not occur at the same elapsed time due to the varying burstcycle, so the ghosts are cancelled out by the ANDing process.

Another problem that can arise by using sensors in a revolving door isinterference caused by echoes or reflections from bursts in one chamberreaching sensors in other chambers. Often, the door wings are formedsolidly, thus preventing interference. In such a case, burst signals A₁through A₈ are sent in any desired fashion, e.g. simultaneously,staggered or sequentially. That is, as shown in FIG. 4C, signals A₁through A₈ are each formed by signal portions I, II, etc. However, ifthe door wings are constructed non-solidly, interference is likely tooccur so it is preferable to send sequential or staggered signals A₁through A₈. That is, A₁ and A₂ are sent to sensors 99a, 99b (e.g. inperiod I), then signals A₃ and A₄ are sent to sensors 99c and 99d (e.g.in period II), followed by signals A₅ and A₆ being sent to sensors 99eand 99f (e.g. in period III), then signals A₇ and A₈ are sent to 99g and99h (e.g. in period IV). This pattern keeps repeating. Sequentialemission avoids detection of echoes due to bursts of sensors in one areaby sensors in another area.

Any reasonable staggered or sequential rotation of sensor operation isacceptable. The stagger or sequence time should be set taking intoaccount the gain of the sensor head and the dimensions of the chambers,as the smaller the chambers and the greater the gain, the more multiplereverberations will be likely to interfere with sensors in otherchambers. Accordingly, the greater the delay time between the activationof sensors in one chamber and activation of sensors in another chamber,the more the reverberations die out. It should be noted that reductionof the gain too much will jeopardize the ability to detect small or softobjects, including reducing the ability to detect card passback.

With reference to FIG. 5, the storage of echoes and the ANDing processwill be explained in more detail. The memory is preferably in the formof multiple storage arrays 101 et seq. Each array has eight columns,each column for storing echoes of a particular sensor. Each bit in eachcolumn corresponds to an amount of time it takes, following a burst fromthat particular sensor, for an echo to return to the sensor. As timecorresponds directly to the distance an object is from the sensor, eachbit in a column also corresponds to a particular distance of an objectfrom the sensor. In the disclosed embodiment, there are sixty-four bitsin each column. If the distance d is 7' (84"), and each bit represents apredetermined incremental distance such as 1.5", fifty-six bitsrepresent 7'. In the preferred embodiment, the sensors are designed tooutput a binary signal, i.e., either an "echo" or a "no echo" signal.The controller 294 keeps track (e.g. by a timer, counter or other means)of how much time has elapsed since a burst, and places the "echo" or "noecho" signal received from the sensor in the appropriate bit for thatamount of time. That is, the controller 294 will take echoes or noechoes and place "1" (echo) or "0" (no echo) in each bit at least up tofifty-six in array 101 for echoes of a first burst, until thefifty-sixth bit is filled. Following a second burst, the controllerfills array 102 in the same way. The process continues until array 10nhas been filled. Then, the controller fills the results array R bylogically ANDing each matching pair of bit and sensor numbers from eacharray 101 through 10n. For example, the value stored in bit 1 for sensor1 in array 101 will be ANDed with the values stored for bit 1 for sensor1 in arrays 102 through 10n, and the result will be stored in bit 1 forsensor 1 in the results array R. If all the first bits are "1", thefirst bit in the results array will have a "1", otherwise it will have a"0".

This logical ANDing process, together with the varying of the burstrepetition rate, (cycle time), removes or at least minimizes the affectof any ghost reflections that get stored in any of the arrays 101through 10n. For example, if cycle times of the burst signals areconstant, the ghost echoes are likely to be stored in coincident bitnumbers in each array 101 through 10n, causing a "1" to be incorrectlystored in the results array R. When the cycle times are varied, ghostsare not likely to coincide, so a false "1" stored in a particular bit inone array will be eliminated during logical ANDing by a "0" in the samebit number in another array. Generally, two arrays are sufficient toeliminate ghosts, but if memory space is available, more arrays ensuregreater reliability. The filling of the storage arrays 101 through 10nand the results array R are all preferably done in real time, but can bedelayed if desired.

Another problem with ultrasonic detectors is that a door panel passingbeneath the sensor returns an echo as would an object or a person in thecompartment. Accordingly, it is necessary to provide the controller 294with a mechanism for distinguishing between a door panel echo and anitem in the compartment. If an echo is returned from some minimumdistance within which the top of the door panel lies, the controllerinterprets the echo as being from a passing door panel and does notundertake security procedures. In FIG. 5, the minimum distance isrepresented by bit number "m" in each array and results array R, whichis shown as the second bit. (In general, the number will depend on thedistance from the sensor to the top of the door panel, and theincremental distance that each bit in an array column represents.) So,when bits 1 and 2 are "0", no door wing is passing by. However, if bit 1and/or 2 is "1", a door wing is assumed to be passing by.

When a door frame has been detected, the system blanks out allresponses, e.g., ignores any further sensor feedback from the sensor(s)for which a door frame has been detected. So, if a "1" is in bit 1 or 2for sensors 99c and 99d (e.g., sensors 3 and 4 in FIG. 5) in array 101,the controller 294 clears all bits in array 101 for sensors 99c and 99d.The same will be true if the controller detects a "1" in bit 1 or 2 inthe next array 102. This clearing process has the effect of creating all"0s" in the results array R for the columns corresponding to the sensors(99c and 99d) where a door frame has been detected, due to the ANDingprocess. If clearing takes place after ANDing, the results array iseither cleared in the corresponding column or ignored for thatcorresponding column.

The clearing process is important to avoid erroneous detection of anobject. When a door frame passes under a sensor, there often arenumerous reflections of an ultrasonic burst between the sensor face andthe top of the door frame. Such reflections would cause "1s" to bestored in the column corresponding to the sensor for several timeperiods in the memory array, which might correspond to three or fourfeet downward into the chamber. Accordingly, it is possible that theseor some of these false "1s" will AND with other false "1s" and cause theresults array to falsely indicate detection of an object. Although thecount in the door position detection system 197 could be used todetermine when door frames are passing particular sensors and theresults array can be ignored for those sensors, the "1s" recorded in thearray 101, 102, . . . , or 10n, might AND with future false "1s" tocreate a false object detection. Clearing only the column correspondingto the sensor detecting a door frame enables random placement of thesensors. Use of array clearing also eliminates any dependence ontolerances in door position detection. Moreover, as the door framepasses the radially outer sensors in fewer burst cycles (and thus fewerdegrees of rotation) than the radially inner sensors, the controllerrecovers faster from door frame passage at the outer sensors. Thus,sensing ability can be recouped relatively quickly, and without thetolerance problems incurred by relying on door position detection.

Controller 294 evaluates the contents of the results array R, and passesthe echo or no echo information to the processor 194 for decision makingregarding empty and non-empty compartments. That is, controller 294preferably sends at least six signals (i.e., six input lines) toprocessor 194.

The first four signals indicate object detection (other than a doorframe) at sensors 99a or 99b, 99c or 99d, 99e or 99f, and 99g or 99h,respectively. Alternatively, a signal could be sent for each sensor. Thefifth and sixth signals indicate object detection by trapped man sensors99i, 99j, respectively. Additional inputs such as a seventh signal toindicate alarm output, tampering with the sensor(s), failed sensor(s),or the like, may be added.

Where the control system is equipped with antipassback (prevention ofcard passback) features such as disclosed in U.S. Pat. No. 4,627,193,object detection can be used to improve the reliability of the system.If an object has not been detected in the authorized chamber by apredetermined amount of rotation of the door wings, such as 90 fromtheir starting position, the processor could stop and reverse the drivesystem, until the door wings are returned to their starting position.For example, if the ID device 110 indicates authorized entry at area 26,at least one of sensors 99g, 99h must indicate an object by the time thedoor wings have moved 90. This antipassback feature can also require atleast one of sensors 99e, 99f to indicate an object at some time betweenwhen the door wings have moved 90° to when they have moved 180°. Thus,even though antipassback normally prevents the same ID device fromrecognizing the same card twice, if the authorized user neglects toenter the door, the ID device where the user inserted the card willstill recognize that card.

With reference to FIG. 6 which is a flowchart of the main operations ofthe processor and controller, an authorized user first inserts a cardinto one of the key card readers 110, 114 to begin operation of thedoor. The device 110 or 114 determines whether the user is authorized(step 6-1), and if so, the processor 194 starts the drive system (step6-2). A variable i is set to 1 (to represent array 101) (step 6-3) andthe processor determines whether the user has passed from the entrypoint to exit point (step 6-4). If so, the drive system is deactivated(step 6-5) by the processor 194 and trapped man sensors 99i and 99j(described below) are activated (step 6-15) by the controller 294. Ifpassage is not complete, the controller sends signals A₁ through A₈ tosensors 99a-99h and the sensors emit ultrasonic energy waves (step 6-6).

In steps 6-7 and 6-8, the echoes (signals B₁ through B₈) are receivedfor each sensor, and stored in array "i". The ANDing process also takesplace to fill or update the results array (step 6-8), as ANDing ispreferably performed in real time. When the results array R isfilled/updated, the controller evaluates the results array to find anyechoes and their distances (step 6-9). This step may involve performingfail-safe functions as discussed in U.S. Pat. No. 4,682,153 (Boozer, etal.), checking the echoes to determine if the floor echo is present, andthe like. Next, the controller 294 determines whether or not a door winghas been detected (by examining the first m bit(s) in each column ofarray "i") (step 6-10), and if a door wing is detected, the clearingoperation is performed (step 611). The controller 294 will clear thecolumns in array "i" which corresponds to any sensors detecting a doorwing. If, as shown in FIG. 6, ANDing has already taken place, thecontroller may also ignore, e.g. inhibit, output for the correspondingcolumns in the results array. Alternatively, ANDing could be delayeduntil after the clearing operation.

The controller 294 may also detect sensor failure or blockage (step6-12), e.g., if a door wing has been detected for a predeterminedminimum amount of time or a door rotation amount, and implement securitymeasures in that case (step 6-17). Such security measures may includeany or all of the following which are appropriate (as in othersituations where security measures are appropriate): stopping furtherprogress of the door, stopping and reversely rotating the door,initiating an alarm, or other appropriate measures. If there is no doorwing detected, or after clearing (with no failure detection), theprocessor 194 examines the inputs (on the first four lines) from thecontroller 294. Whether or not a chamber is authorized or unauthorizedis determined by the processor 194 using outputs from identificationdevice 110 or 114 such as in U.S. Pat. No. 4,627,193, or other suitablemeans. That is, authorized entry at area 24 will be relayed by theidentification device 114 to the processor 194, which will thenrecognize signals from sensors 99c or 99d (line 2 in FIG. 3), and 99a or99b (line 1) as authorized, and sensors 99e or 99f (line 3) and 99g or99h (line 4) as unauthorized. (The opposite is true for authorized entryindicated by device 110.) Accordingly, the processor knows whichchambers are authorized and which are unauthorized for use in step 6-13.If there are echoes in unauthorized chambers, security measures aretaken.

In the case where object detection is used to supplement an antipassbackfeature, the processor performs step 6-14. That is, the processor checksfor echoes in authorized chambers by using the information on lines 1-4,the inputs of devices 110 and 114, and the input of the positiondetection system 197 to determine if echoes have been received in theauthorized chambers by the predetermined amount of time or amount ofdoor rotation. If echoes have not been received in authorized chambers,security measures are implemented (step 6-17). If there are no echoes inunauthorized areas, and there are echoes in the authorized areas (orthere is no antipassback feature), then the controller 294 nextdetermines which storage array will be updated in response to echoesfrom the next burst to be generated. This is done by determining whetherthe storage array "i" that has just been filled is the last one (i=n)(step 6-18). If array "i" is the last one, "i" is set to one (step 6-3)so that the first array 101 has its contents replaced by the echoes inresponse to the next burst. If the storage array that has just beenfilled is not the last array 10n, then "i" is incremented by 1 (step6-19), so that the next array has its contents replaced. Thus, thecontents of each array are successively updated, and the contents of theresults array are updated each time a storage array has been updated.

Sensor failure or blockage may be detected in several ways. If sensorsare all positioned such that all (or some) door wings will align withthe sensors at the same time, the processor or controller can simplycheck the results array at the first and second bits for each sensor (orthe ones which will align) to determine if there is a "1" in at leastone of the first and second bits for each sensor. If all the sensors donot show a "1" in at least one of the first two bits, tampering,malfunction or other problem could be assumed. Another method ismeasuring the amount of time that the first two bits contain at leastone "1", and assuming there is a sensor malfunction, jammed door ortampering if the predetermined time for the door to pass the sensor hasbeen exceeded. In such a case, an alarm is triggered or buildingsecurity is notified.

The range "d" to which the echo receive time is set is based on acompromise between optimum coverage and avoiding noise caused by echoesfrom the floor which can occur due primarily to changes in the velocityof sound with temperature. That is, as temperature increases, thevelocity of sound increases causing the floor to appear to move upward.The shift in apparent floor position is about 0.1% per degreeFahrenheit. For a 10' floor-to-ceiling distance, there is a shift ofabout 1' per 100° F.

In accordance with a further feature of the invention, the range iscontrollable. As shown in FIG. 3 and step 6-8, five DIP switches 81through 85 set the range, each switch representing an incrementalincrease in the range. For example, switch 81 is 48", switch 82 is 24",switch 83 is 12", switch 84 is 6" and switch 85 is 3", so that turningon all the switches results in a 93" range. If the ceiling height is 8'(96"), the recommended maximum range is 7' (84") as discussed above. Areasonable minimum range is two-thirds of the door height (i.e., 64").These DIP switches are shown connected to the controller 294 but couldalternatively be inputted to the processor 194.

In response to the setting on the DIP switches, the controllerdetermines how many bits in each column of the arrays to fill (or to payattention to). For example, an 84" setting corresponds to 56 bits, and a72" setting is 48 bits. The optimal maximum distance setting (set by theDIP switches) can be lengthened if real time temperature compensation isused. Such compensation is performed by measuring the floor echo returntime (i.e., the apparent distance of the floor) and correcting for anychanges from the expected time distance). This processing can beperformed in any "dead time," e.g., during the time between bursts,after the last bit in the array has been filled. Other processing, suchas running software timers and finding any failed sensors can beperformed in the "dead time" too.

As shown in step 6-15, trapped man sensors 99i and 99j operate followingand at times other than authorized passage, in case an item or person istrapped in or enters a compartment at other than the entrance or exit.These sensors are the same as the sensors 99a through 99h, and arecontrolled in the same way as sensors 99a through 99h. A single memoryarray or multiple memory arrays may be used for these sensors 99i, 99j,and the ANDing process may also be used. When a trapped item or personis detected (step 6-16), security measures (step 6-14) are taken,including any of notifying a guard, triggering an alarm, inhibiting doormovement, reversing the door or other appropriate measures.

The disclosed embodiment is only an illustration of the invention, andis not intended to limit the scope of the invention as defined in theappended claims. For example, instead of a separate processor andcontroller, the control system can include just onemicroprocessor/controller to perform all of these functions, such asrepresented by the dashed line box 494 in FIG. 3.

What is claimed is:
 1. A control system for a security door of the typehaving a housing with a first portal and a second portal, a door memberrotatably disposed in the housing and having a plurality of wings which,in cooperation with the housing, define a plurality of compartmentsmoveable between the first and second portals in response to rotation ofthe door member, the control system comprising:means for rotating thedoor member to move a selected compartment from one of the first andsecond portals to the other of the first and second portals; sensingmeans disposed in the housing for emitting energy waves into the housingbetween the first and second portals, for detecting echoes of the energywaves due to any objects of persons in the housing and outputting asignal indicative of an echo or no echo; detection means for determiningthe position of the selected compartment; and controller means,connected to the sensing means and to the detection means, for drivingthe sensing means and the means for rotating in response toidentification of an authorized user, and for detecting passage of anyobjects or persons in any of the compartments other than the selectedcompartment based on the position of the selected compartment and thedetection of any echoes by the sensing means, wherein the sensing meanscomprises multiple sensors, each of the sensors receiving a drivingsignal from the controller means for generating successive bursts ofwaves, wherein the bursts occur at varying cycle times.
 2. The controlsystem for a security door as recited in claim 1, wherein the controllermeans is further adapted for stopping movement of the selectedcompartment between the first and second portals when no echoes aredetected by the sensing means located along the path of the selectedcompartment.
 3. The control system for a security door as recited inclaim 1, wherein the control system further comprises additional sensingmeans, disposed in the housing and operable when the means for rotatingis in a nonoperative state, for detecting the presence of any objects orpersons in compartments located at positions other than the first andsecond portals.
 4. A method for controlling a security door of a typehaving a housing with a first portal and a second portal, a door memberrotatably disposed in the housing and having a plurality of wings which,in cooperation with the housing, define a plurality of compartmentsmoveable between the first and second portals in response to rotation ofthe door member, the method comprising the steps of:rotating the doormember to move a selected compartment from one of the first and secondportals to the other of the first and second portals in response toidentification of an authorized user; emitting bursts of energy wavesinto the housing between the first and second portals, and detectingechoes of the energy waves due to any objects or persons in the housing;and determining the position of the selected compartment, and preventingpassage of any objects or persons detected in compartments other thanthe selected compartment as determined by the position of the selectedcompartment and detection of any echoes, wherein any echoes detectedwithin a predetermined time following emission of an energy wave areignored.
 5. The method as recited in claim 4, wherein echoes detectedfrom the door member wings are ignored.
 6. The method as recited inclaim 4, wherein the energy waves are emitted from sensors drivensequentially.
 7. The method as recited in claim 4, wherein movement ofthe selected compartment between the first and second portals is stoppedand reversed when no echoes are detected.
 8. The method as recited inclaim 4, further comprising a step of detecting the presence of anyobjects or persons in compartments located at positions other than thefirst and second portals when the door member is in a non-operativestate.
 9. A control system for a security door of the type having ahousing with a first portal and a second portal, a door member rotatablydisposed in the housing and having a plurality of wings which, incooperation with the housing, define a plurality of compartmentsmoveable between the first and second portals in response to rotation ofthe door member, the control system comprising:means for rotating thedoor member to move a selected compartment from one of the first andsecond portals to the other of the first and second portals; sensingmeans disposed in the housing for emitting energy waves into the housingbetween the first and second portals, for detecting echoes of the energywaves due to any objects or persons in the housing and outputting asignal indicative of an echo or no echo; detection means for determiningthe position of the selected compartment; and controller means,connected to the sensing means and to the detection means, for drivingthe sensing means and the means for rotating in response toidentification of an authorized user, and for detecting passage of anyobjects or persons in any of the compartments other than the selectedcompartment based on the position of the selected compartment and thedetection of any echoes by the sensing means, wherein the controllermeans further comprises means for ignoring any echoes detected from thedoor member as the door member wings pass by the sensing means, themeans for ignoring including means for identifying when the door memberwings are passing by the sensing means based on whether any echoes arereceived within a predetermined elapsed time following emission of anenergy wave by the sensing means.
 10. A control system for a securitydoor of the type having a housing with a first portal and a secondportal, a door member rotatably disposed in the housing and having aplurality of wings which, in cooperation with the housing, define aplurality of compartments moveable between the first and second portalsin response to rotation of the door member, the control systemcomprising:means for rotating the door member to move a selectedcompartment form one of the first and second portals to the other of thefirst and second portals; sensing means disposed in the housing foremitting energy waves into the housing between the first and secondportals, for detecting echoes of the energy waves due to any objects orpersons in the housing and outputting a signal indicative of an echo orno echo; detection means for determining the position of the selectedcompartment; and controller means, connected to the sensing means and tothe detection means, for driving the sensing means and the means forrotating in response to identification of an authorized user, and fordetecting passage of any objects or persons in any of the compartmentsother than the selected compartment based on the position of theselected compartment and the detection of any echoes by the sensingmeans, wherein the controller means has a memory associated therewithfor digitally storing an indication of one of a detected echo and nodetected echo for each of a selected number of bits in the memory, eachbit corresponding to a predetermined distance from the sensing means, sothat the selected number of bits corresponds to a predetermined rangefrom the sensing means.
 11. The control system for a security door asrecited in claim 10, wherein the sensing means comprises multipleultrasonic sensors, the memory comprises an array having the selectednumber of bits for each sensor, and each of the sensors receives adriving signal from the controller means for generating successivebursts of ultrasonic waves.
 12. The control system for a security dooras recited in claim 11, wherein the memory comprises multiple arrays,and the controller means further comprises means for logically ANDingcorresponding bits in each array for each sensor, and storing theresults in an additional array in memory.
 13. The control system for asecurity door as recited in claim 12, wherein the bursts occur atvarying cycle times.
 14. The control system for a security door asrecited in claim 12, wherein the controller means further comprisesmeans for clearing any echoes from all of the bits, associated with eachsensor for which a detected echo is stored in an array in at least onepredetermined bit for that sensor in that array.
 15. The control systemfor a security door as recited in claim 10, wherein the sensing meanscomprises multiple ultrasonic sensors driven sequentially.
 16. Thecontrol system for a security door as recited in claim 10, wherein thecontroller means further comprises means for changing the selectednumber of bits to adjust the predetermined range from the sensing means.17. A control system for a security door of the type having a housingwith a first portal and a second portal, a door member rotatablydisposed in the housing and having a plurality of wings which, incooperation with the housing, define a plurality of compartmentsmoveable between the first and second portals in response to rotation ofthe door member, the control system comprising:means for rotating thedoor member to move a selected compartment from one of the first andsecond portals to the other of the first and second portals; sensingmeans disposed in the housing for emitting energy waves into the housingbetween the first and second portals, for detecting echoes of the energywaves due to any objects or persons in the housing and outputting asignal indicative of an echo or no echo; detection means for determiningthe position of the selected compartment; and controller means,connected to the sensing means and to the detection means, for drivingthe sensing means and the means for rotating in response toidentification of an authorized user, and for detecting passage of anyobjects or persons in any of the compartments other than the selectedcompartment based on the position of the selected compartment and thedetection of any echoes by the sensing means, wherein the controllermeans generates a gain clock signal, and the sensing means includesmeans for incrementally increasing a gain of the sensing means, the gainof the sensing means being reset by each burst.
 18. A method forcontrolling a security door of a type having a housing with a firstportal and a second portal, a door member rotatably disposed in thehousing and having a plurality of wings which, in cooperation with thehousing, define a plurality of compartments moveable between the firstand second portals in response to rotation of the door member, themethod comprising the steps of:rotating the door member to move aselected compartment from one of the first and second portals to theother of the first and second portals in response to identification ofan authorized user; emitting bursts of energy waves into the housingbetween the first and second portals, and detecting echoes of the energywaves due to any objects or persons in the housing; and determining theposition of the selected compartment, and preventing passage of anyobjects or persons detected in compartments other than the selectedcompartment as determined by the position of the selected compartmentand detection of any echoes, wherein the energy waves are emitted fromsensors, and each of the sensors is driven at a varying cycle time. 19.The method as recited in claim 18, wherein the sensors are drivensequentially.
 20. A method for controlling a security door of a typehaving a housing with a first portal and a second portal, a door memberrotatably disposed in the housing and having a plurality of wings which,in cooperation with the housing, define a plurality of compartmentsmoveable between the first and second portals in response to rotation ofthe door member, the method comprising the steps of:rotating the doormember to move a selected compartment from one of the first and secondportals to the other of the first and second portals in response toidentification of an authorized user; emitting bursts of energy wavesfrom a sensor into the housing between the first and second portals, anddetecting echoes of the energy waves with the sensor due to any objectsor persons in the housing; and determining the position of the selectedcompartment, and preventing passage of any objects or persons detectedin compartments other than the selected compartment as determined by theposition of the selected compartment and detection of any echoes,wherein an indication of one of a detected echo and no detected echo isstored in a memory for each bit of a selected number of bits in thememory, each bit corresponding to a predetermined distance from thesensor, so that the selected number of bits corresponds to apredetermined range from the sensor.
 21. The method as recited in claim20, wherein multiple ultrasonic sensors are used, and the energy wavesare ultrasonic waves.
 22. The method as recited in claim 21, wherein theechoes or no echoes detected are stored in the memory separately foreach sensor, the memory having at least two arrays circularly arranged,and each successive array is filled in response to the echoes or noechoes detected following each successive burst.
 23. The method asrecited in claim 22, wherein corresponding bits in each array for eachsensor are logically ANDed and stored in an additional array updatedafter each successive burst, and a person or object is detected only ifa bit in the additional array contains an indication of an echo.
 24. Themethod as recited in claim 23, further comprising the step of clearingall bits associated with any sensor in the array, which has detected anecho within a predetermined time of a burst.
 25. The method as recitedin claim 23, wherein each of the sensors is driven at a varying cycletime.
 26. The method as recited in claim 20, wherein the selected numberof bits is changeable for adjusting the predetermined range.
 27. Amethod for controlling a security door of a type having a housing with afirst portal and a second portal, a door member rotatably disposed inthe housing and having a plurality of wings which, in cooperation withthe housing, define a plurality of compartments moveable between thefirst and second portals in response to rotation of the door member, themethod comprising the steps of:rotating the door member to move aselected compartment from one of the first and second portals to theother of the first and second portals in response to identification ofan authorized user; emitting bursts of energy waves from a sensor intothe housing between the first and second portals, and detecting echoesof the energy waves with the sensor due to any objects or persons in thehousing; and determining the position of the selected compartment, andpreventing passage of any objects or persons detected in compartmentsother than the selected compartment as determined by the position of theselected compartment and detection of any echoes, wherein a gain of thesensor is increased incrementally after each burst, and reset by asubsequent burst.